Sustained oscillations of 13-18 Hz were observed in local field potentials (LFPs) in the cerebellar cortex of a behaving monkey. These oscillations, which appeared to be generated in the granular cell layer, were particularly prominent in the paramedian lobule. The oscillatory activity decreased during drowsiness or extreme arousal and occurred most often when the animal was immobile but alert. In a task requiring the animal to move the arm approximately 1 s after an auditory cue, the oscillations stopped some 150-200 ms after the cue, resumed 200-300 ms later, and stopped again 50-100 ms before movement onset. This modulation pattern was observed with consistency only when the animal responded reliably to the auditory cue. The results suggest that the cerebellum could be involved in some higher level of integration particularly during complex sensorimotor behavior.
Cerebellar local field potential (LFP) oscillations were recorded in the paramedian lobule of one hemisphere, while monkeys were in two behavioral conditions: actively performing an elbow flexion-extension or a lever-press task in response to an auditory or visual stimulus to get reward (active condition), or waiting quietly for the reward to come in the same time window after the appearance of the stimulus (passive condition). The oscillations in the paramedian lobule were first characterized in four monkeys, and they showed an idiosyncratic frequency for each monkey, between 13 and 25 Hz. The granule cell layer multi-unit activity was phase-locked with the negative phase of the LFP oscillations, while Purkinje cell simple spikes were also sometimes phase-locked with the LFP. Three monkeys were trained to perform the motor tasks: the LFP oscillations were modulated, in the active condition, in a systematic manner in relation to the lever-press or elbow flexion-extension tasks. During periods when the monkey was waiting to initiate movement, LFP oscillations appeared and then stopped with movement initiation. This modulation was valid for the task being executed with either hand. Surprisingly, the LFP oscillations were also systematically modulated during the passive condition; as the monkey was waiting for the usual time to get a reward passively, oscillations appeared stronger and were stopped by the end of the usual delay, whether the monkey was rewarded or not. This type of modulation was not affected by the length of the stimulus, as long as the reward window was known to the monkey. If the monkey had not been previously trained to the active condition, the modulation appeared in the passive condition. These results show that cerebellar LFP oscillations in the paramedian lobule are reliably present when the monkey is involved in a waiting period, whether this period ends with an active or passive event. This study provides electrophysiological evidence for a specific pattern of activity in the cerebellum for the expectancy of events that are known to be bound to happen, either externally, or from voluntary action.
Only 35 per cent of residents agreed to participate in the study, but the similarity of the results in each of the six hospitals suggests that they are reliable. Although supervision was always available, 72 per cent of the interventions were performed autonomously, possibly because the residents appreciate and learn from that experience. Time on call is not the best time for learning procedures, as there were too few opportunities to perform them. These results suggest that the pedagogical objectives of the call system should be re-evaluated with special attention to autonomy and self-confidence. Procedures should be learned in other settings.
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